This invention relates to a novel zoom lens and image pickup apparatus, and more particularly to a zoom lens which has a macro mode and an image pickup apparatus in which the zoom lens is used.
In recent years, image pickup apparatus which use a solid-state image pickup device such as digital still cameras have been and are being popularized. Above all, together with the popularization of digital still cameras, a zoom lens is demanded which is superior in compactness and has a macro mode which can implement a high image pickup magnifying power while it covers a wide range from the very wide angle side to the telephoto side by means of the single lens.
Conventionally, various types of zoom lenses which have a macro mode have been proposed. For example, Japanese Patent Laid-open No. Hei 1-298307 (hereinafter referred to as Patent Document 1) discloses a zoom lens wherein a first lens group is used for focusing in an ordinary region and a plurality of lens groups different from the first lens group are moved independently of each other in the direction of an optical axis to perform focusing in a macro region thereby to achieve a high magnifying power. However, to an image pickup apparatus of the lens-integration type having an automatic focusing function which has a great angle of field and uses a contrast detection system, it is not preferable to perform focusing in an ordinary region using the first lens group. Further, it is not preferable to use different lens groups to perform focusing in an ordinary region and focusing in a macro region because this complicates the mechanism.
Japanese Patent Laid-open No. Hei 11-235232 (hereinafter referred to as Patent Document 2) discloses a zoom lens which solves of the problems of the zoom lens of Patent Document 1 described above and is used optimally with an image pickup apparatus which uses a contrast detection system. According to the zoom lens of Patent Document 2, the second and third groups of a four-group zoom lens having positive, negative, positive and positive refracting powers are moved to obtain a macro region. Further, not only in the ordinary region but also in the macro region, the fourth lens group is used for focusing.